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D N Chernov

Publications and source records attributed to D N Chernov.

11 recordsLinked to original sources
PubMed1999

Telomerase activity of cells during alterations of their proliferative states.

We showed that the telomerase activity (TAC) of human promyelocytic leukemic cells U-937 and HL-60 sharply decreased after induction of macrophagal differentiation. Dedifferentiation which occurred several days after removing the inductor was accompanied by the resumption of proliferation and increase of TAC. Telomerase activity significantly decreased also when U-937 cells ceased to proliferate in response to long-term inhibition of the telomerase function by azidothymidine. TAC was observed to decrease slowly for 6-8 days in the course of transition of mouse fibroblasts 3T3 Swiss to the quiescent state. TAC decreased both in serum-deprived cells and in slowly proliferating high-density inhibited cells. During the exit from quiescence and in dedifferentiation, the increase in TAC preceded the resumption of proliferation. In all the cases described the alterations of TAC correlated with alterations in the nonspecific polymerase activity which we had found earlier (D. N. Chernov, Y. E. Yegorov, and S. S. Akimov, DokL Biochemistry 349:55-58 (1996)). The problems of TAC regulation are discussed.

3T3 Cells↗
PubMed1997

[Azidothymidine, blocking telomerase functioning, shortens telomeric repeats in transformed human cells].

The long-term action of azidothymidine, reverse transcriptase inhibitor, on cultivated U-937 (human promyelocyte leukemia) and MeWo (human melanoma) cells led to the concentration-dependent decrease in the length of telomeric chromosomal repeats. Telomere shortening was accompanied by temporary retardation of cell proliferation. Combined with the data obtained previously, these results suggest that azidothymidine inhibits telomerase functioning in cultivated cells.

Cell Division↗
PubMed1997

Blockade of telomerase function by nucleoside analogs.

Two types of spontaneously transformed cells appear in the culture of senescent mouse embryonic fibroblasts. The first type are cells with restricted proliferative potential (up to 30 population doublings); the other type are immortalized cells. Cells of the first type, unlike those of the second, have no telomerase activity and undergo two rounds of senescence. Spontaneous transformation of mouse embryonic fibroblasts in the presence of the reverse transcriptase inhibitors azidothymidine and carbovir led to the formation of telomerase-free clones. A fraction of these clones have the ability to overcome senescence via the acquisition of high telomerase activity. Cells with a very high level of telomerase activity become resistant to azidothymidine and carbovir. Azidothymidine-induced artificial senescence of rat myoblasts in culture resembles the senescence of fibroblasts, but the resulting cells acquire sharp morphological peculiarities. The blockade of telomerase function by azidothymidine in human U-937 and MeWo cells leads to the shortening of telomeres, but does not result in senescence. A hypothesis of the generation of the signal that induces senescence is proposed. This hypothesis suggests a change in DNA conformation during telomere shortening as a result of a change of loop structure of telomeric chromatin.

Animals↗
PubMed1996

Modified nucleotides as substrates and inhibitors of adenylate kinase from different sources.

The substrate and inhibitory properties of modified nucleotides with respect to adenylate kinase from rabbit muscles, human placenta and Escherichia coli were studied. A number of 5'-hydrogenphosphonates and 5'-fluorophosphates of modified nucleotides were shown to inhibit the phosphorylation reaction catalyzed by these enzymes. A clear difference between phosphonates of 3'-deoxyribonucleotides and the corresponding ribo- and 2',3'-dideoxyribonucleotides was found. 3'-Azido-2',3'-dideoxythymidine and its phosphorus derivatives did not inhibit the adenylate kinase reaction.

Adenylate Kinase↗
PubMed1996

Reverse transcriptase inhibitors suppress telomerase function and induce senescence-like processes in cultured mouse fibroblasts.

Spontaneous transformation of mouse embryonic fibroblasts in the presence of the reverse transcriptase inhibitors azidothymidine and carbovir led to the formation of telomerase-free clones. After prolonged cultivation of fibroblasts in the presence of carbovir, resistant cells with a very high level of telomerase activity were obtained. Azidothymidine and carbovir, but not dideoxycytidine, induced senescence-like processes in cultures of immortal mouse fibroblasts. After long-term incubation, cell proliferation gradually decreased, their morphology becoming similar to that of the senescent ones. The process was reversible: after inhibitor removal, the cells, including the giant ones, entered mitoses. All these data suggest that reverse transcriptase inhibitors block telomerase function in mouse cells.

3T3 Cells↗
PubMed1996

Should the asymmetry of enzymatic active centers always correlate with the asymmetry of their substrates?

Analysis of the substrate specificity of DNA polymerases and in part some other enzymes of nucleic acid metabolism towards unnatural L-stereomeric nucleosides and nucleotides was made. As a result, the hypothesis is proposed that when the chiral part of the substrate molecule does not interact specifically with the enzyme, substitution of natural D enantiomers by L compounds is possible.

Binding Sites↗
PubMedDate not supplied

[Reverse transcriptase of the human immunodeficiency virus: isolation and substrate specificity].

Human immunodeficiency virus (HIV-I) reverse transcriptase was expressed in E. coli and purified to homogeneity (E. coli strain RRI (pRC-RT, pRK 248cIts)). We have investigated the substrate properties toward to DNA synthesis, catalyzed by this enzyme, of some nucleoside-5'-triphosphate analogues, previously studied in the same reactions, catalyzed by AMV and M-MLV reverse transcriptases. We have investigated substrate properties of new analogues of 2',3'-dideoxy-2',3'-didehydro- and 2',3'-dideoxytubercidin-5'-triphosphates. We have compared the relative efficiency of incorporation of different analogues tested in the DNA chain. It has been shown that expressed and purified HIV reverse transcriptase had the same specificity to analogues of 2'-deoxyribonucleoside-5'-triphosphates as was described for reverse transcriptases and natural HIV reverse transcriptase as well. These properties allow to apply the expressed HIV reverse transcriptase in different model systems.

Base Sequence↗